The Facts on Atrial Fibrillation

The heart is divided into four chambers: two atria on top and two ventricles underneath. The role of the atria is to fill the ventricles with blood, which is then pumped to the lungs or to the rest of the body.

The normal beating of the heart is controlled by electrical signals sent from a particular segment of heart tissue called the sinus node. The sinus node acts as the heart's natural pacemaker. It is found near the top of the right atrium. Normally, the sinus node sends an electrical pulse that travels down the muscle tissue to the atrioventricular (AV) node (acting like a "toll booth"), which determines how many impulses are allowed to then pass to the ventricles.

An arrhythmia occurs when the heart's regular rhythm becomes irregular – it may speed up or slow down. Many arrhythmias exist, but those originating from the ventricles are generally more serious than from the atria.

Atrial fibrillation (AF) is one type of arrhythmia. Instead of the sinus node controlling the heart rate, different parts of the atria fire at the same time. This causes the atria to fibrillate, which is an uncoordinated quivering of the muscle. The atria pump blood less effectively but well enough to allow the ventricles to function. The irregular heartbeat is due to rapid beating of the atria (usually more than 350 beats per minute), and the irregular movement of the electrical signals through the AV node. Instead of every electrical signal being allowed through to the ventricles only certain electrical signals are allowed to pass.

AF is potentially dangerous because blood can pool in the atrium, which increases the risk that a blood clot will form. If this clot travels to the brain, it will cause a stroke. AF is the most common form of all harmful arrhythmias, affecting 6% of those over the age of 65, and the risk increases to 10% to 15% in people over 80. Men are more likely than women to be hospitalized for atrial fibrillation.

AF may be present in a number of different forms:

paroxysmal AF: recurrent temporary condition that starts suddenly and then after a period of time (usually less than 7 days), the heart returns to a normal heartbeat without medical assistance

persistent AF: the heart beats irregularly and requires medical assistance to return to a normal rhythm. This type of AF tends to last more than 7 days.

permanent AF: the heart has an irregular rhythm that cannot return to normal with medication or other treatments

All three situations carry equal risk of blood clot formation.

Are you at risk for a stroke?

Every 10 minutes on average, a Canadian has a stroke. Could you be next? There are many things that increase your risk of a stroke (called stroke risk factors).

Causes of Atrial Fibrillation

The cause of AF is not always known, but possible causes can include any of the following:

abnormal structure of the heart

diseases that damage the valves of the heart

high blood pressure

thyroid disease

diabetes

heart failure

previous stroke or transient ischemic attack (TIA)

binge drinking

increasing age

Knowing what factors can trigger an episode of atrial fibrillation, such as intense exercise, extreme emotion, or excessive alcohol intake, may help people to be proactive in their self-management of this condition.

Symptoms and Complications of Atrial Fibrillation

Some people do not experience any symptoms. In this case, their doctor may recognize the condition during a regular medical examination.

When symptoms of AF are present, they typically include:

palpitations

chest discomfort

rapid and irregular heartbeat

lightheadedness or, in rare cases, fainting

dizziness

shortness of breath – this may occur at rest in more severe cases of AF

weakness

reduced ability to exercise

People with AF who have right-sided heart failure may also have swelling of the arms and legs, weight gain, or ascites (abdominal swelling due to accumulation of fluid). This is a severe type of AF that requires immediate medical attention.

Everyone knows what it feels like to experience an occasional flutter of the heart, and usually it does not mean anything. See your doctor if you experience chest pains, feel faint, or notice your pulse to be faster than usual or irregular over a prolonged period.

AF is a progressive condition that can weaken the heart and its ability to pump blood, especially if it is not treated properly. Another possible complication of AF is the formation of blood clots that can cause a stroke. The risk of stroke depends on your age and other risk factors, but the presence of AF increases your risk of having a stroke by at least 5 times.

The contents of this site are for informational purposes only and are meant to be discussed with your physician or other qualified health care professional before being acted on. Never disregard any advice given to you by your doctor or other qualified health care professional. Always seek the advice of a physician or other licensed health care professional regarding any questions you have about your medical condition(s) and treatment(s). This site is not a substitute for medical advice.